Vox AC-15 Acting Weird

My AC-15 (British made KORG) is fading in and out volume-wise as I play. I've heard of this happening before. Where should I start my troubleshooting?

Does it fade slow or quick? How often? Tubes are always the first place to start.

After tubes you could check speaker cable, volume pot after that it gets tedious trying to find a loose connection or failed component.

I was in a hurry when I originally posted. I was at the library and was being timed out. I warmed it up and plugged in the guitar. Played a little and then it started fading slowly until it started distorting a bit. Then it came back up. It went through that cycle over a couple of songs, so I turned it off until I had more time to mess with it. I've heard of this problem in AC-15's before, but I can't remember what the problem was.

I'll check the basics go from there. It does have a preamp out so I can isolate things a bit.

I was in a hurry when I originally posted. I was at the library and was being timed out. I warmed it up and plugged in the guitar. Played a little and then it started fading slowly until it started distorting a bit. Then it came back up. It went through that cycle over a couple of songs, so I turned it off until I had more time to mess with it. I've heard of this problem in AC-15's before, but I can't remember what the problem was.

I'll check the basics go from there. It does have a preamp out so I can isolate things a bit.Are filter caps getting really really hot? Any smoke?

Start with the power tubes- that sounds exactly like a dying power tube to me.

I had the same issues, and I tought it was time to take my amp to a tech. With a few money he replaced the tube (the original one - 35 years old! - was exhausted and microphonic) and cleaned all the jacks & pots. It's more than OK now, it's fantastic.

If it's new I'd take it back. Especially if you got it at Guitar Center. Other wise I'd try replacing the tubes first.

is the trem on? :lol: :grin: :lol:

No, it's not new, it's about seven years old and no, the trem is not on. :wink: The cycle is much slower then that. I may have another pair of EL 84's around and give them a try.
Thanks for the suggestions.

I got the amp out, put it on the bench and cleaned the jacks and worked the volume pot back and forth a bunch of times to clean off any gunk. After plugging in the Tele I played for two hours without a problem. I got so lost in the sound that I forgot all about fixing anything. How can I fix what's not broke? Man, a Tele and a Vox are a nice combination. Especially when the tubes get warmed up. :grin:

It lives in a dusty room, so I put a towel over it when I was done to keep dust out of the pots and controls.

I got the amp out, put it on the bench and cleaned the jacks and worked the volume pot back and forth a bunch of times to clean off any gunk. After plugging in the Tele I played for two hours without a problem. I got so lost in the sound that I forgot all about fixing anything. How can I fix what's not broke? Man, a Tele and a Vox are a nice combination. Especially when the tubes get warmed up. :grin:

It lives in a dusty room, so I put a towel over it when I was done to keep dust out of the pots and controls.

If it happens again...

One possibility is that the heaters are being deprived of power.

This could happen if you have a dry joint somewhere so as the amp heats up, the heater voltage vanishes and the volume drops off.